CN116686291A

CN116686291A - Sub-block cross-component linear model prediction

Info

Publication number: CN116686291A
Application number: CN202280008260.6A
Authority: CN
Inventors: 李翎; 李翔; 陈联霏; 刘杉
Original assignee: Tencent America LLC
Current assignee: Tencent America LLC
Priority date: 2021-10-05
Filing date: 2022-09-21
Publication date: 2023-09-01
Also published as: WO2023059984A1; EP4201065A4; KR20230065344A; EP4201065A1; US20230106614A1; JP2024508459A

Abstract

In one method, encoded information of a current block in a current picture is received from an encoded video bitstream. The current block may be partitioned into a plurality of sub-blocks. A first flag included in the encoded information may be obtained, wherein the first flag indicates whether cross-component linear model prediction (CCLM) is applied to a current block, wherein chroma samples of the current block are predicted based on reconstructed luma samples of the current block. Responsive to a first flag indicating that a CCLM is applied to a current block, respective predicted sample values of the chroma samples in each of the plurality of sub-blocks of the current block are determined based on the CCLM. Reconstructing the current block based on the respective predicted sample values of chroma samples in each of the plurality of sub-blocks of the current block.

Description

Sub-block cross-component linear model prediction

Incorporation of reference

The present application claims priority to "subblock cross component linear model prediction" from U.S. patent application No. 17/946,299, filed on day 2022, month 9, and 16, which claims priority to "subblock cross component linear model prediction" from U.S. provisional application No. 63/252,395, filed on day 2021, month 10, and 5. The disclosure of the prior application is incorporated herein by reference in its entirety.

Technical Field

This disclosure describes embodiments that relate generally to video encoding and decoding.

Background

The background description provided herein is intended to generally represent the background of the application. Work of the presently named inventors, to the extent it is described in this background section as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

Inter picture prediction with motion compensation may be used for video encoding and decoding. The uncompressed digital video may include a series of pictures, each having a spatial dimension of, for example, 1920 x 1080 luma samples and associated chroma samples. The series of pictures has a fixed or variable picture rate (informally also referred to as frame rate), such as 60 pictures per second or 60Hz. Uncompressed video has specific bit rate requirements. For example, 1920×1080p60:2:0 video at 8 bits per sample (1920×1080 luma sample resolution at 60Hz frame rate) requires a bandwidth close to 1.5 Gbit/s. One hour of such video requires more than 600GB of memory space.

One purpose of video encoding and decoding is to reduce redundant information of an input video signal by compression. Video compression may help reduce the bandwidth and/or storage requirements described above, in some cases by two or more orders of magnitude. Lossless compression and lossy compression, as well as combinations of both, may be employed. Lossless compression refers to a technique that reconstructs an exact copy of the original signal from the compressed original signal. When lossy compression is used, the reconstructed signal may be different from the original signal, but the distortion between the original signal and the reconstructed signal is small enough to make the reconstructed signal available for the intended application. In the case of video, lossy compression is widely used. The amount of allowable distortion depends on the application; for example, some users consuming streaming applications may tolerate higher distortion than users of television distribution applications. The compression ratio may reflect: higher allowable/tolerable distortion may result in higher compression ratios.

Video encoders and decoders can utilize techniques from a number of broad categories, including, for example, motion compensation, transformation, quantization, and entropy coding.

Video codec techniques may include known intra-coding techniques. In intra coding, sample values are represented without reference to samples or other data of a previously reconstructed reference picture. In some video codecs, a picture is spatially subdivided into blocks of samples. When all sample blocks are encoded in intra mode, the picture may be an intra picture. Intra pictures and their derivatives (e.g., independent decoder refresh pictures) may be used to reset the decoder state and thus may be used as the first picture in an encoded video bitstream and video session, or as a still image. The samples of the intra block may then be transformed and the transform coefficients may be quantized prior to entropy encoding. Intra prediction may be a technique that minimizes sample values in the pre-transform domain. In some cases, the smaller the transformed DC value and the smaller the AC coefficient, the fewer bits are needed to represent the block after entropy encoding at a given quantization step size.

As is known from techniques such as MPEG-2 generation coding, conventional intra coding does not use intra prediction. However, some newer video compression techniques include: the attempt is made based on, for example, surrounding sample data and/or metadata that are acquired during spatially adjacent encoding and/or decoding and that precede the data block in decoding order. Such techniques are hereinafter referred to as "intra-prediction" techniques. Note that in at least some cases, intra prediction uses only reference data from the current picture in reconstruction, and not reference data from the reference picture.

There may be many different forms of intra prediction. When more than one such technique can be applied in a given video coding technique, the technique used may be codec in intra-prediction mode. In some cases, the modes may have sub-modes and/or parameters, and these may be encoded separately or contained in a mode codeword. For a given mode, sub-mode and/or parameter combination, which codeword to use may have an impact on the coding efficiency gain through intra prediction, and so may the entropy coding technique used to convert the codeword into a code stream.

Some mode of intra prediction is introduced along with h.264, modified in h.265, and further modified in newer coding techniques such as joint detection mode (JEM), general video coding (VVC), and reference set (BMS). The predictor block may be formed using neighboring sample values that belong to already available. For example, sample values of neighboring samples may be copied into a predictor block according to one direction. The reference to the direction of use may be encoded in the code stream or may itself be predicted.

Referring to fig. 1, depicted at the bottom right is a subset of 9 predictor directions known among the 33 possible predictor directions of h.265 (33 angle modes corresponding to 35 intra modes). The point (101) where the arrows converge represents the sample being predicted. The arrow indicates the direction from which the samples are predicted. For example, arrow (102) indicates that samples (101) are predicted from one or more samples at an upper right angle of 45 degrees to horizontal. Similarly, arrow (103) indicates that samples (101) are predicted from one or more samples at the lower left of samples (101) at an angle of 22.5 degrees to horizontal.

Still referring to fig. 1, a square block (104) comprising 4 x 4 samples (indicated by the thick dashed line) is shown at the top left. The square block (104) consists of 16 samples, each marked with an "S" and its position in the Y dimension (e.g., row index) and its position in the X dimension (e.g., column index). For example, sample S21 is the second sample in the Y dimension (from the top) and the first sample in the X dimension (from the left). Similarly, sample S44 is the fourth sample in block (104) in both the Y dimension and the X dimension. Since the block is a 4×4-sized sample, S44 is located in the lower right corner. Reference samples following a similar numbering scheme are also shown. The reference samples are marked with an "R" and their Y position (e.g., row index) and X position (e.g., column index) relative to the block (104). In h.264 and h.265, the prediction samples are adjacent to the block under reconstruction; so negative values need not be used.

Intra-picture prediction may be implemented by copying reference sample values from neighboring samples assigned to the signaled prediction direction. For example, assume that the encoded video bitstream includes signaling indicating, for the block, a prediction direction consistent with arrow (102) -that is, predicting samples from one or more prediction samples at an upper right angle of 45 degrees to the horizontal direction. In such a case, samples S41, S32, S23, and S14 are predicted from the same reference sample R05. Sample S44 is then predicted from the reference sample R08.

In some cases, the values of multiple reference samples may be combined, for example by interpolation, to calculate the reference samples, especially when the direction is not exactly divisible by 45 degrees.

As video coding technology advances, the number of possible directions increases. In h.264 (2003), 9 different directions can be represented. This increases to 33 in h.265 (2013), and JEM/VVC/BMS can support up to 65 directions at the time of this disclosure. Experiments have been performed to identify the most probable directions and some techniques in entropy coding can be used to represent those probable directions with a small number of bits, accepting some cost for less probable directions. Furthermore, the direction itself may sometimes be predicted from the neighboring direction for the decoded block.

Fig. 2 shows a schematic diagram (201) depicting 65 intra prediction directions according to JEM to illustrate the increase in the number of prediction directions over time.

Mapping bits representing intra-prediction directions in an encoded video stream may vary with different video encoding techniques; and may be, for example, a simple direct mapping from the prediction direction to intra prediction modes, to codewords, to complex adaptation schemes involving the most probable modes, and similar techniques. However, in all cases, there may be certain directions in the video content that are statistically less likely to occur than certain other directions. Since the goal of video compression is to reduce redundancy, in a well-functioning video coding technique, those less likely directions will be represented by a greater number of bits than more likely directions.

Disclosure of Invention

Aspects of the present disclosure provide methods and apparatus for video encoding/decoding. In some examples, an apparatus for video decoding includes a receiving circuit and a processing circuit.

According to one aspect of the present disclosure, a method of video decoding performed in a video decoder is provided. In the method, encoded information of a current block in a current picture may be received from an encoded video bitstream. The current block may be partitioned into a plurality of sub-blocks. A first flag included in the encoded information may be obtained, wherein the first flag indicates whether cross-component linear model prediction (CCLM) is applied to a current block, wherein chroma samples of the current block are predicted based on reconstructed luma samples of the current block. In response to the first flag indicating that a CCLM is applied to a current block, a respective predicted sample value for the chroma samples in each of the plurality of sub-blocks of the current block may be determined based on the CCLM. The current block may also be reconstructed based on the respective predicted sample values of the chroma samples in each of the plurality of sub-blocks of the current block.

In one example, the current block is partitioned into the plurality of sub-blocks in a width direction based on a width of the current block being equal to or greater than a height of the current block.

In another example, the current block is partitioned into the plurality of sub-blocks in a height direction based on a width of the current block being smaller than a height of the current block.

In yet another example, the current block is partitioned into the plurality of sub-blocks having a minimum sub-block size in a height direction and a width direction.

In this method, a syntax element in the encoded information may be acquired. The minimum sub-block size may be determined based on the syntax element. The syntax element is in one of a Sequence Parameter Set (SPS), a Picture Parameter Set (PPS), a slice, and a tile.

In some embodiments, the prediction sample values of the chroma samples in a second sub-block of the plurality of sub-blocks are determined based on reconstructed samples of a first sub-block of the plurality of sub-blocks, wherein the second sub-block is adjacent to the first sub-block.

In some embodiments, a second flag included in the encoded information is acquired in response to the first flag indicating that the CCLM is applied to the current block. The second flag indicates whether CCLM is applied to each of the plurality of sub-blocks. In response to the second flag indicating that the CCLM is applied to each of the plurality of sub-blocks, the respective predicted sample values of the chroma samples in each of the plurality of sub-blocks of the current block are determined based on the CCLM.

In some embodiments, the predicted sample values of the chroma samples in a first sub-block of the plurality of sub-blocks are determined based on a first pattern of the CCLM in response to a reconstructed neighboring sample being adjacent to a left side of the first sub-block, wherein the first pattern of the CCLM indicates: the predicted sample values of the chroma samples in the first sub-block are determined based on the reconstructed neighboring samples that are neighboring the left side of the first sub-block. In response to reconstructed neighboring samples being adjacent to a left side and a top side of a second sub-block of the plurality of sub-blocks, determining the predicted sample values of the chroma samples in the second sub-block of the plurality of sub-blocks based on a second mode of the CCLM, wherein the second mode of the CCLM indicates the predicted sample values of the chroma samples in the second sub-block are determined based on the reconstructed neighboring samples being adjacent to the left side and the top side of the second sub-block.

In some embodiments, a second flag included in the encoded information is obtained in response to the first flag indicating that the CCLM is applied to the current block, wherein the second flag indicates whether the CCLM is applied to each of the plurality of sub-blocks. An index included in the encoded information is obtained, wherein the index indicates a CCLM mode of the CCLM. The CCLM mode indicates which reconstructed neighboring samples the CCLM applies to generate the respective predicted sample values for the chroma samples in each of the plurality of sub-blocks. Responsive to a second flag indicating that CCLM is applied to each of the plurality of sub-blocks and an index indicating the CCLM mode, a respective predicted sample value of the chroma samples in each of the plurality of sub-blocks of the current block is determined based on the CCLM using the CCLM mode.

In some embodiments, in response to the index indicating a first CCLM mode, the respective predicted sample values of the chroma samples in each of the plurality of sub-blocks are determined based on reconstructed neighboring samples that are adjacent to a left side and a top side of the respective one of the plurality of sub-blocks. In response to the index indicating a second CCLM mode, the respective predicted sample value of the chroma samples in each of the plurality of sub-blocks is determined based on the reconstructed neighboring samples that are neighboring the left side of the respective one of the plurality of sub-blocks. In response to the index indicating a third CCLM mode, the respective predicted sample value of the chroma samples in each of the plurality of sub-blocks is determined based on the reconstructed neighboring samples neighboring the top side of the respective one of the plurality of sub-blocks.

According to another aspect of the present disclosure, an apparatus is provided. The apparatus includes a processing circuit. The processing circuitry may be configured to perform any method for video encoding and decoding.

Aspects of the present disclosure also provide a non-transitory computer-readable medium storing instructions that, when executed by a computer for video encoding, cause the computer to perform any of the methods for video encoding.

Drawings

Other features, properties and various advantages of the disclosed subject matter will become more apparent from the following detailed description and drawings.

Fig. 1 is a schematic diagram of an exemplary subset of intra prediction modes.

Fig. 2 is a diagram of an exemplary intra prediction direction.

Fig. 3 is a schematic diagram of a simplified block diagram of a communication system (300) according to an embodiment.

Fig. 4 is a schematic diagram of a simplified block diagram of a communication system (400) according to an embodiment.

Fig. 5 is a schematic diagram of a simplified block diagram of a decoder according to an embodiment.

Fig. 6 is a schematic diagram of a simplified block diagram of an encoder according to an embodiment.

Fig. 7 shows a block diagram of an encoder according to another example embodiment.

Fig. 8 shows a block diagram of a decoder according to another example embodiment.

Fig. 9 is an exemplary illustration of cross-component linear model (CCLM) prediction, according to some embodiments of the present disclosure.

FIG. 10A is a first exemplary block partition in CCLM prediction according to some embodiments of the present disclosure.

FIG. 10B is a second exemplary block partition in CCLM prediction according to some embodiments of the present disclosure.

FIG. 10C is a third exemplary block partition in CCLM prediction according to some embodiments of the present disclosure.

FIG. 10D is a fourth exemplary block partition in CCLM prediction according to some embodiments of the present disclosure.

Fig. 11 shows a flowchart outlining an exemplary decoding method in accordance with some embodiments of the present disclosure.

Fig. 12 shows a flowchart outlining an exemplary encoding method according to some embodiments of the present disclosure.

FIG. 13 is a schematic diagram of a computer system according to one embodiment.

Detailed Description

Fig. 3 is a simplified block diagram of a communication system (300) according to an embodiment of the present disclosure. The communication system (300) comprises a plurality of terminal devices which can communicate with each other via, for example, a network (350). For example, the communication system (300) includes a first pair of terminal devices (310) and (320) interconnected by a network (350). In the embodiment of fig. 3, the first pair of terminal apparatuses (310) and (320) performs unidirectional data transmission. For example, the terminal device (310) may encode video data, such as a video picture stream acquired by the terminal device (310), for transmission over the network (350) to another terminal device (320). The encoded video data is transmitted in one or more encoded video code streams. The terminal device (320) may receive the encoded video data from the network (350), decode the encoded video data to recover the video data, and display the video pictures according to the recovered video data. Unidirectional data transmission is common in applications such as media services.

In another embodiment, the communication system (300) includes a second pair of terminal devices (330) and (340) that perform bi-directional transmission of encoded video data, such as may occur during a video conference. For bi-directional data transmission, each of the terminal device (330) and the terminal device (340) may encode video data (e.g., a video picture stream collected by the terminal device) for transmission over the network (350) to the other of the terminal device (330) and the terminal device (340). Each of the terminal device (330) and the terminal device (340) may also receive encoded video data transmitted by the other of the terminal device (330) and the terminal device (340), and may decode the encoded video data to recover the video data, and may display a video picture on an accessible display device according to the recovered video data.

In the embodiment of fig. 3, the terminal device (310), the terminal device (320), the terminal device (330), and the terminal device (340) may be interpreted as servers, personal computers, and smart phones, but the principles of the present disclosure are not limited thereto. Embodiments of the present disclosure use laptop computers, tablet computers, media players, and/or dedicated video conferencing devices. The network (350) represents any number of networks that communicate encoded video data between the terminal devices (310), 320, 330, and 340), including, for example, wired (or connected) and/or wireless communication networks. The communication network (350) may exchange data in circuit-switched and/or packet-switched channels. The network may include a telecommunications network, a local area network, a wide area network, and/or the internet. For the purposes of the present application, the architecture and topology of the network (350) may be irrelevant to the operation of the present disclosure unless otherwise explained below.

As an example, fig. 4 shows the placement of a video encoder and video decoder in a video streaming environment. The presently disclosed subject matter is equally applicable to other video-enabled applications including, for example, video conferencing, digital TV, compressed video storage on digital media including CDs, DVDs, memory sticks, etc.

The streaming system may include an acquisition subsystem (413), which may include a video source (401), such as a digital camera, creating, for example, an uncompressed video picture stream (402). In an embodiment, a video picture stream (402) includes samples acquired by a digital camera. Compared to the encoded video data (404) (or encoded video code stream (404)), the uncompressed video picture stream (402) is depicted as a bold line to emphasize a high data volume video picture stream, the video picture stream (402) can be processed by an electronic device (420), the electronic device (420) comprising a video encoder (403) coupled to a video source (401). The video encoder (403) may include hardware, software, or a combination of hardware and software to implement or implement aspects of the disclosed subject matter as described in more detail below. Compared to the video picture stream (402), the encoded video data (404) (or encoded video code stream (404)) is depicted as a thin line to emphasize the lower data amount of the encoded video data (404) (or encoded video code stream), which may be stored on a streaming server (405) for future use. One or more streaming client sub-systems, such as client sub-system (406) and client sub-system (408) in fig. 4, may access streaming server (405) to retrieve copies (407) and copies (409) of encoded video data (404). The client subsystem (406) may include, for example, a video decoder (410) in an electronic device (430). A video decoder (410) decodes an incoming copy (407) of the encoded video data and generates an output video picture stream (411) that can be presented on a display (412) (e.g., a display screen) or another presentation device (not depicted). In some streaming systems, encoded video data (404), video data (407), and video data (409) (e.g., a video bitstream) may be encoded according to some video encoding/compression standard. Examples of such standards include ITU-T H.265. In an embodiment, the video coding standard being developed is informally referred to as next generation video coding (Versatile Video Coding, VVC), and the present application may be used in the context of the VVC standard.

It should be noted that the electronic device (420) and the electronic device (430) may include other components (not shown). For example, the electronic device (420) may include a video decoder (not shown), and the electronic device (430) may also include a video encoder (not shown).

Fig. 5 is a block diagram of a video decoder (510) according to an embodiment of the present disclosure. The video decoder (510) may be disposed in an electronic device (530). The electronic device (530) may include a receiver (531) (e.g., a receiving circuit). A video decoder (510) may be used in place of the video decoder (410) in the embodiment of fig. 4.

The receiver (531) may receive one or more encoded video sequences to be decoded by the video decoder (510); in the same embodiment or another embodiment, one encoded video sequence at a time, wherein the decoding of each encoded video sequence is independent of the other encoded video sequences. The encoded video sequence may be received from a channel (501), which may be a hardware/software link to a storage device storing encoded video data. The receiver (531) may receive encoded video data as well as other data, e.g. encoded audio data and/or auxiliary data streams, which may be forwarded to entities (not shown) that they each use. The receiver (531) may separate the encoded video sequence from other data. To prevent network jitter, a buffer memory (515) may be coupled between the receiver (531) and the entropy decoder/parser (520) (hereinafter "parser (520)"). In some applications, the buffer memory (515) may be part of the video decoder (510). In other applications, the buffer memory (515) may be disposed external (not shown) to the video decoder (510). While in other applications a buffer memory (not shown) is provided outside the video decoder (510), for example to prevent network jitter, a further buffer memory (515) may be present inside the video decoder (510), for example to handle playout timing. The buffer memory (515) may not be needed or may be made smaller when the receiver (531) receives data from a store/forward device with sufficient bandwidth and controllability or from an isochronous network. Of course, for use on a traffic packet network such as the internet, a buffer memory (515) may be required, which may be relatively large. Such buffer memory may advantageously be of adaptive size and may be implemented at least in part in an operating system or similar element (not labeled) external to the video decoder (510).

The video decoder (510) may include a parser (520) to reconstruct the symbols (521) from the encoded video sequence. The categories of these symbols include information for managing the operation of the video decoder (510), as well as potential information to control a display device (512) (e.g., a display screen) that is not an integral part of the electronic device (530), but that may be coupled to the electronic device (530), as shown in fig. 5. The control information for the display device may be a supplemental enhancement information (Supplemental Enhancement Information, SEI) message or a parameter set fragment (not labeled) of video availability information (Video Usability Information, VUI). A parser (520) may parse/entropy decode the received encoded video sequence. The encoding of the encoded video sequence may be in accordance with video encoding techniques or standards, and may follow various principles, including variable length encoding, huffman coding (Huffman coding), arithmetic coding with or without context sensitivity, and so forth. The parser (520) may extract a sub-group parameter set for at least one of the sub-groups of pixels in the video decoder from the encoded video sequence based on the at least one parameter corresponding to the group. A subgroup may include a group of pictures (Group of Pictures, GOP), pictures, tiles, slices, macroblocks, coding Units (CUs), blocks, transform Units (TUs), prediction Units (PUs), and so forth. The parser (520) may also extract information, such as transform coefficients, quantizer parameter values, motion vectors, etc., from the encoded video sequence.

The parser (520) may perform entropy decoding/parsing operations on the video sequence received from the buffer memory (515), thereby creating symbols (521).

Depending on the type of encoded video picture or a portion of encoded video picture (e.g., inter and intra pictures, inter and intra blocks), and other factors, the reconstruction of the symbol (521) may involve a number of different units. Which units are involved and how are controlled by subgroup control information that a parser (520) parses from the encoded video sequence. For clarity, such sub-group control information flow between the parser (520) and the units below is not described.

In addition to the functional blocks already mentioned, the video decoder (510) may be conceptually subdivided into several functional units as described below. In practical embodiments operating under commercial constraints, many of these units interact tightly with each other and may be integrated with each other. However, for the purposes of describing the disclosed subject matter, the conceptual subdivision of functional units is appropriate below.

The first unit may be a scaler/inverse transform unit (551). A scaler/inverse transform unit 551 receives quantized transform coefficients as symbols 521 and control information including information of which type of inverse transform, block size, quantization factor, quantization scaling matrix, etc. is used from a parser 520. The sealer/inverse transform unit (551) may output a block comprising sample values, which may be input into the aggregator (555).

In some cases, the output samples of the scaler/inverse transform unit (551) may belong to an intra-coded block; for example, blocks of predictive information from previously reconstructed portions of the current picture may be used, without using predictive information from previously reconstructed pictures. Such predictive information may be provided by an intra picture prediction unit (552). In some cases, the intra picture prediction unit (552) uses the surrounding reconstructed information fetched from the current picture buffer (558) to generate a surrounding block of the same size and shape as the block being reconstructed. For example, the current picture buffer (558) buffers partially reconstructed current pictures and/or fully reconstructed current pictures. In some implementations, the aggregator (555) adds, on a per sample basis, prediction information generated by the intra picture prediction unit (552) to the output sample information provided by the scaler/inverse transform unit (551).

In other cases, the output samples of the scaler/inverse transform unit (551) may belong to inter-coding and potential motion compensation blocks. In this case, the motion compensated prediction unit (553) may access the reference picture memory (557) to extract samples for prediction. After motion compensation of the extracted samples according to the symbol (521), these samples may be added by an aggregator (555) to the output of a sealer/inverse transform unit (551), in this case referred to as residual samples or residual signals, generating output sample information. The retrieval of the prediction samples by the motion compensated prediction unit (553) from an address within the reference picture memory (557) may be controlled by a motion vector, and the motion vector is used by the motion compensated prediction unit (553) in the form of the symbol (521), which symbol (521) for example comprises X, Y and a reference picture component. The motion compensation may also include interpolation of sample values extracted from the reference picture store (557) when sub-sample accurate motion vectors are used, the motion compensation may include motion vector prediction mechanisms, and so on.

The output samples of the aggregator (555) may be employed by various loop filtering techniques in a loop filter unit (554). Video compression techniques may include in-loop filter techniques that are controlled by parameters included in an encoded video sequence (also referred to as an encoded video stream), and that are available to a loop filter unit (556) as symbols (521) from a parser (520). However, in other embodiments, the video compression techniques may also be responsive to meta information obtained during decoding of a previous (in decoding order) portion of an encoded picture or encoded video sequence, as well as to previously reconstructed and loop filtered sample values.

The output of the loop filter unit (556) may be a stream of samples, which may be output to a display device (512) and stored in a reference picture memory (557) for use in subsequent inter picture prediction.

Once fully reconstructed, some encoded pictures may be used as reference pictures for future prediction. For example, once an encoded picture corresponding to a current picture is fully reconstructed and the encoded picture is identified (by, for example, a parser (520)) as a reference picture, the current picture buffer (558) may become part of a reference picture memory (557) and a new current picture buffer may be reallocated before starting to reconstruct a subsequent encoded picture.

The video decoder (510) may perform decoding operations according to a predetermined video compression technique, for example, in the ITU-T h.265 standard. The coded video sequence may conform to the syntax specified by the video compression technique or standard used in the sense that the coded video sequence follows the syntax of the video compression technique or standard and the configuration files recorded in the video compression technique or standard. In particular, a profile may select some tools from all tools available in a video compression technology or standard as the only tools available under the profile. It is also necessary for compliance that the complexity of the encoded video sequence be within the limits defined by the hierarchy of video compression techniques or standards. In some cases, the hierarchy limits a maximum picture size, a maximum frame rate, a maximum reconstructed sample rate (measured in units of, for example, mega samples per second), a maximum reference picture size, and so on. In some cases, the limits set by the hierarchy may be further defined by hypothetical reference decoder (Hypothetical Reference Decoder, HRD) specifications and metadata managed by an HRD buffer signaled in the encoded video sequence.

In one embodiment, the receiver (531) may receive additional (redundant) data along with the encoded video. The additional data may be part of the encoded video sequence. The additional data may be used by a video decoder (510) to properly decode the data and/or more accurately reconstruct the original video data. The additional data may be in the form of, for example, a temporal, spatial, or signal-to-noise ratio (signal noise ratio, SNR) enhancement layer, redundant slices, redundant pictures, forward error correction codes, and the like.

Fig. 6 is a block diagram of a video encoder (603) according to an embodiment of the present disclosure. The video encoder (603) is disposed in the electronic device (620). The electronic device (620) includes a transmitter (640) (e.g., a transmission circuit). The video encoder (603) may be used in place of the video encoder (403) in the embodiment of fig. 4.

The video encoder (603) may receive video samples from a video source (601) (not part of the electronic device (620) in the fig. 6 embodiment) that may acquire video images to be encoded by the video encoder (603). In another embodiment, the video source (601) may be part of an electronic device (620).

The video source (601) may provide a source video sequence in the form of a stream of digital video samples to be encoded by the video encoder (603), which may have any suitable bit depth (e.g., 8 bits, 10 bits, 12 bits … …), any color space (e.g., bt.601Y CrCB, RGB … …), and any suitable sampling structure (e.g., Y CrCB4:2:0, Y CrCB 4:4:4). In a media service system, a video source (601) may be a storage device capable of storing previously prepared video. In a video conferencing system, the video source (601) may be a camera that collects local image information as a video sequence. Video data may be provided as a plurality of individual pictures that are given motion when viewed in sequence. The picture itself may be implemented as a spatial pixel array, where each pixel may include one or more samples, depending on the sampling structure, color space, etc. being used. The relationship between pixels and samples can be readily understood by those skilled in the art. The following focuses on describing the sample.

According to an embodiment, the video encoder (603) may encode and compress pictures of the source video sequence into an encoded video sequence (643) in real time or under any other temporal constraint required by the application. Performing the proper encoding speed is a function of the controller (650). In some embodiments, a controller (650) controls and is functionally coupled to other functional units as described below. For clarity, coupling is not shown. The parameters set by the controller (650) may include rate control related parameters (picture skip, quantizer, lambda value for rate distortion optimization techniques, etc.), picture size, picture group (group of pictures, GOP) layout, maximum motion vector search range allowed, etc. The controller (650) may be used to have other suitable functions related to a video encoder (503) optimized for a certain system design.

In some embodiments, the video encoder (603) operates in a coding loop. As a simple description, in an embodiment, the encoding loop may include a source encoder (630) (e.g., responsible for creating symbols, such as a symbol stream, based on the input picture and reference picture to be encoded) and a (local) decoder (633) embedded in the video encoder (603). In addition, the decoder (633) reconstructs the symbols to create sample data in a manner similar to the way the (remote) decoder created the sample data (since any compression between the symbols and the encoded video stream is lossless in the video compression technique contemplated by the present application). The reconstructed sample stream (sample data) is input to a reference picture memory (634). Since decoding of the symbol stream produces a bit-accurate result independent of the decoder location (local or remote), the content in the reference picture memory (634) is also bit-accurate between the local encoder and the remote encoder. In other words, the reference picture samples "seen" by the prediction portion of the encoder are exactly the same as the sample values "seen" when the decoder would use prediction during decoding. This reference picture synchronicity basic principle (and drift generated in case synchronicity cannot be maintained due to channel errors, for example) is also used in some related art.

The operation of the "local" decoder (633) may be the same as, for example, the "remote" decoder of the video decoder (510) that has been described in detail above in connection with fig. 5. However, referring briefly to fig. 5 in addition, when a symbol is available and the entropy encoder (645) and the decoder (520) are able to losslessly encode/decode the symbol into an encoded video sequence, the entropy decoding portion of the video decoder (510), including the buffer memory (515) and the decoder (520), may not be implemented entirely in the encoder's local decoder (633).

In this connection it is observed that in addition to the parsing/entropy decoding present in the decoder, any decoder technique must also be present in the corresponding encoder in substantially the same functional form. For this reason, the disclosed subject matter focuses on decoder operation. The descriptions of encoder techniques may be abbreviated as their inverse to the fully described decoder techniques. A more detailed description is required only in certain areas and is provided below.

During operation, in some embodiments, the source encoder (630) may perform motion compensated predictive encoding. The motion compensated predictive coding predictively codes an input picture with reference to one or more previously coded pictures from a video sequence designated as "reference pictures". In this way, the encoding engine (632) encodes differences between pixel blocks of an input picture and pixel blocks of a reference picture, which may be selected as a prediction reference for the input picture.

The local video decoder (633) may decode encoded video data of a picture, which may be designated as a reference picture, based on the symbol created by the source encoder (630). The operation of the encoding engine (632) may be a lossy process. When encoded video data may be decoded at a video decoder (not shown in fig. 6), the reconstructed video sequence may typically be a copy of the source video sequence with some errors. The local video decoder (633) replicates the decoding process that may be performed on the reference picture by the video decoder and may cause the reconstructed reference picture to be stored in the reference picture cache (634). In this way, the video encoder (603) may locally store a copy of the reconstructed reference picture that has common content (no transmission errors) with the reconstructed reference picture to be acquired by the far-end video decoder.

The predictor (635) may perform a prediction search for the encoding engine (632). That is, for a new picture to be encoded, the predictor (635) may search the reference picture memory (634) for sample data (as candidate reference pixel blocks) or some metadata, such as reference picture motion vectors, block shapes, etc., that may be suitable prediction references for the new picture. The predictor (635) may operate on a block of samples by block of pixels to find a suitable prediction reference. In some cases, from the search results obtained by the predictor (635), it may be determined that the input picture may have prediction references derived from a plurality of reference pictures stored in the reference picture memory (634).

The controller (650) may manage the encoding operations of the source encoder (630) including, for example, setting parameters and subgroup parameters for encoding video data.

The outputs of all of the above functional units may be entropy encoded in an entropy encoder (645). An entropy encoder (645) losslessly compresses symbols generated by the various functional units according to techniques such as huffman coding, variable length coding, arithmetic coding, etc., thereby converting the symbols into an encoded video sequence.

The transmitter (640) may buffer the encoded video sequence created by the entropy encoder (645) in preparation for transmission over a communication channel (660), which may be a hardware/software link to a storage device that is to store encoded video data. The transmitter (640) may combine the encoded video data from the video encoder (603) with other data to be transmitted, such as encoded audio data and/or an auxiliary data stream (source not shown).

The controller (650) may manage the operation of the video encoder (603). During encoding, the controller (650) may assign each encoded picture a certain encoded picture type, but this may affect the encoding techniques applicable to the respective picture. For example, a picture may generally be assigned to any one of the following picture types:

An intra picture (I picture), which may be a picture that can be encoded and decoded without using any other picture in the sequence as a prediction source. Some video codecs allow for different types of intra pictures, including, for example, independent decoder refresh (Independent Decoder Refresh, "IDR") pictures. Variations of the I picture and its corresponding applications and features are known to those skilled in the art.

A predictive picture (P-picture), which may be a picture that may be encoded and decoded using intra-or inter-prediction that predicts sample values for each block using at most one motion vector and a reference index.

Bi-predictive pictures (B-pictures), which may be pictures that can be encoded and decoded using intra-or inter-prediction that predicts sample values for each block using at most two motion vectors and a reference index. Similarly, multiple predictive pictures may use more than two reference pictures and associated metadata for reconstructing a single block.

A source picture may typically be spatially subdivided into blocks of samples (e.g., blocks of 4 x 4, 8 x 8, 4 x 8, or 16 x 16 samples), and encoded block by block. These blocks may be predictive coded with reference to other (coded) blocks, which are determined from the coding allocation applied to the respective pictures of the blocks. For example, a block of an I picture may be non-predictive encoded, or the block may be predictive encoded (spatial prediction or intra prediction) with reference to an already encoded block of the same picture. The pixel blocks of the P picture may be prediction encoded by spatial prediction or by temporal prediction with reference to a previously encoded reference picture. A block of B pictures may be prediction encoded by spatial prediction or by temporal prediction with reference to one or two previously encoded reference pictures.

The video encoder (603) may perform encoding operations according to a predetermined video encoding technique or standard, such as the ITU-T h.265 recommendation. In operation, the video encoder (603) may perform various compression operations, including predictive coding operations that exploit temporal and spatial redundancies in the input video sequence. Thus, the encoded video data may conform to the syntax specified by the video encoding technique or standard used.

In an embodiment, the transmitter (640) may transmit the additional data when transmitting the encoded video. The source encoder (630) may take such data as part of the encoded video sequence. The additional data may include temporal/spatial/SNR enhancement layers, redundant pictures and slices, other forms of redundant data, SEI messages, VUI parameter set slices, and the like.

The acquired video may be used as a plurality of source pictures (video pictures) in a time series. Intra picture prediction (often abbreviated as intra prediction) exploits spatial correlation in a given picture, while inter picture prediction exploits (temporal or other) correlation between pictures. In an embodiment, a specific picture being encoded/decoded is divided into blocks, and the specific picture being encoded/decoded is referred to as a current picture. When a block in the current picture is similar to a reference block in a reference picture that has been previously encoded and still buffered in video, the block in the current picture may be encoded by a vector called a motion vector. The motion vector points to a reference block in a reference picture, and in the case of using multiple reference pictures, the motion vector may have a third dimension that identifies the reference picture.

In some embodiments, bi-prediction techniques may be used for inter-picture prediction. According to bi-prediction techniques, two reference pictures are used, e.g., a first reference picture and a second reference picture, both preceding a current picture in video in decoding order (but possibly in display order in the past and future, respectively). The block in the current picture may be encoded by a first motion vector pointing to a first reference block in a first reference picture and a second motion vector pointing to a second reference block in a second reference picture. In particular, the blocks may be jointly predicted by a combination of the first reference block and the second reference block.

Furthermore, merge mode techniques may be used in inter picture prediction to improve coding efficiency.

According to some embodiments of the present disclosure, prediction such as inter-picture prediction and intra-picture prediction is performed in units of blocks. For example, according to the HEVC standard, pictures in a sequence of video pictures are partitioned into Coding Tree Units (CTUs) for compression, with CTUs in the pictures having the same size, such as 64 x 64 pixels, 32 x 32 pixels, or 16x16 pixels. In general, a CTU includes three coding tree blocks (coding tree block, CTB): one luminance CTB and two chrominance CTBs. Still further, each CTU may be split into one or more Coding Units (CUs) in a quadtree. For example, a 64×64 pixel CTU may be split into one 64×64 pixel CU, or 4 32×32 pixel CUs, or 16 16×16 pixel CUs. In one embodiment, each CU may be analyzed to determine a prediction type for the CU, such as an inter prediction type or an intra prediction type. Furthermore, depending on temporal and/or spatial predictability, a CU is split into one or more Prediction Units (PUs). In general, each PU includes a luminance Prediction Block (PB) and two chrominance PB. In an embodiment, a prediction operation in encoding (encoding/decoding) is performed in units of prediction blocks. Using a luminance prediction block as an example of a prediction block, the prediction block includes a value matrix (e.g., luminance value) of pixels (e.g., 8x8 pixels, 16x16 pixels, 8x16 pixels, 16x8 pixels, etc.).

Fig. 7 is a diagram of a video encoder (703) according to another embodiment of the present disclosure. A video encoder (703) is for receiving a processing block (e.g., a prediction block) of sample values within a current video picture in a sequence of video pictures and encoding the processing block into an encoded picture that is part of the encoded video sequence. In this embodiment, a video encoder (703) is used in place of the video encoder (303) in the embodiment of fig. 4.

In one HEVC example, a video encoder (703) receives a matrix of sample values for a processing block, such as a prediction block of 8 x 8 samples. The video encoder (703) uses, for example, rate-distortion optimization (rate-distortion optimization) to determine whether to encode the processing block using intra-mode, inter-mode, or bi-prediction mode. When encoding a processing block in intra mode, the video encoder (703) may use intra prediction techniques to encode the processing block into the encoded picture; and when it is determined to encode the processing block in inter mode or bi-predictive mode, the video encoder (703) may encode the processing block into the encoded picture using inter prediction or bi-predictive techniques, respectively. In some video coding techniques, the merge mode may be a sub-mode of inter picture prediction, in which motion vectors are derived from one or more motion vector predictors without resorting to coded motion vector components outside the predictor. In some other video codec techniques, there may be motion vector components that are applicable to the subject block. In one example, the video encoder (703) includes other components, such as a mode decision module (not shown) for determining the mode of the processing block.

In the embodiment of fig. 7, the video encoder (703) includes an inter-frame encoder (730), an intra-frame encoder (722), a residual calculator (723), a switch (726), a residual encoder (724), a general controller (721), and an entropy encoder (725) coupled together as shown in fig. 7.

An inter-frame encoder (730) is used to receive samples of a current block (e.g., a processing block), compare the block to one or more of the reference blocks (e.g., blocks in a previous picture and a subsequent picture), generate inter-frame prediction information (e.g., redundancy information description, motion vectors, merge mode information according to inter-frame coding techniques), and calculate inter-frame prediction results (e.g., prediction blocks) based on the inter-frame prediction information using any suitable technique. In some embodiments, the reference picture is a decoded reference picture that is decoded based on the encoded video information.

An intra encoder (722) is used to receive samples of a current block (e.g., process the block), in some cases compare the block to blocks encoded in the same picture, generate quantization coefficients after transformation, and in some cases also generate intra prediction information (e.g., according to intra prediction direction information of one or more intra coding techniques). An intra encoder (722) calculates an intra prediction result (e.g., a prediction block) based on intra prediction information and a reference block in the same picture.

A general controller (721) is used to determine general control data and to control other components of the video encoder (703) based on the general control data. In an embodiment, a general purpose controller (721) determines the mode of the block and provides a control signal to a switch (726) based on the mode. For example, when the mode is an intra mode, the general controller (721) controls the switch (726) to select an intra mode result for use by the residual calculator (723) and controls the entropy encoder (725) to select intra prediction information and add the intra prediction information in a bitstream; and when the mode is an inter mode, the general controller (721) controls the switch (726) to select an inter prediction result for use by the residual calculator (723), and controls the entropy encoder (725) to select inter prediction information and add the inter prediction information in a bitstream.

A residual calculator (723) calculates a difference (residual data) between the received block and a prediction result selected from an intra-frame encoder (722) or an inter-frame encoder (730). A residual encoder (724) is used to encode residual data to generate transform coefficients. In an embodiment, a residual encoder (724) is configured to operate based on residual data to convert the residual data from the time domain to the frequency domain to generate transform coefficients. The transform coefficients are then processed through quantization to obtain quantized transform coefficients. In various exemplary embodiments, the video encoder (703) further comprises a residual decoder (728). A residual decoder (728) is used to perform an inverse transform and generate decoded residual data. The decoded residual data may be suitably used by an intra encoder (722) and an inter encoder (730). For example, the inter-encoder (730) may generate a decoded block based on the decoded residual data and the inter-prediction information, and the intra-encoder (722) may generate a decoded block based on the decoded residual data and the intra-prediction information. The decoded blocks are processed appropriately to generate decoded pictures, and the decoded pictures may be buffered in a memory circuit (not shown) and used as reference pictures in some embodiments.

An entropy encoder (725) is used to format the code stream to produce encoded blocks. The entropy encoder (725) is configured to include various information according to a suitable standard, such as the HEVC standard. In an embodiment, the entropy encoder (725) is configured to obtain general control data, selected prediction information (e.g., intra prediction information or inter prediction information), residual information, and other suitable information in the bitstream. It should be noted that, according to the subject matter of the present disclosure, when a block is encoded in an inter mode or a merge sub-mode of a bi-prediction mode, there is no residual information.

Fig. 8 is a diagram of a video decoder (810) according to another embodiment of the present disclosure. A video decoder (810) is configured to receive encoded pictures that are part of an encoded video sequence and decode the encoded pictures to generate reconstructed pictures. In an embodiment, a video decoder (810) is used in place of the video decoder (410) in the embodiment of fig. 4.

In the fig. 8 embodiment, video decoder (810) includes entropy decoder (871), inter decoder (880), residual decoder (873), reconstruction module (874), and intra decoder (872) coupled together as shown in fig. 8.

The entropy decoder (871) may be used to reconstruct certain symbols from the encoded pictures, the symbols representing syntax elements that make up the encoded pictures. Such symbols may include, for example, modes used to encode the block (e.g., intra mode, inter mode, bi-prediction mode, the latter two in a merge sub-mode or another sub-mode), prediction information (e.g., intra prediction information or inter prediction information) that may identify certain samples or metadata used by the intra decoder (872) or inter decoder (880), respectively, to predict, residual information in the form of, for example, quantized transform coefficients, and so forth. In an embodiment, when the prediction mode is an inter or bi-directional prediction mode, providing inter prediction information to an inter decoder (880); and providing intra prediction information to an intra decoder (872) when the prediction type is an intra prediction type. The residual information may be quantized via inverse quantization and provided to a residual decoder (873).

An inter decoder (880) is configured to receive inter prediction information and generate an inter prediction result based on the inter prediction information.

An intra decoder (872) is configured to receive intra-prediction information and generate a prediction result based on the intra-prediction information.

A residual decoder (873) is configured to perform inverse quantization to extract dequantized transform coefficients, and process the dequantized transform coefficients to transform a residual from a frequency domain to a spatial domain. The residual decoder (873) may also need some control information (to obtain the quantizer parameter QP), which may be provided by the entropy decoder (871) (data path not labeled, since this is only low data volume control information).

A reconstruction module (874) is used to combine the residual output by the residual decoder (873) with the prediction result (which may be output by the inter prediction module or the intra prediction module) in the spatial domain to form a reconstructed block that forms part of a reconstructed picture that may be part of the reconstructed video. It should be noted that other suitable operations, such as deblocking operations, may be performed to improve visual quality.

It should be noted that video encoder (403), video encoder (603), and video encoder (703), as well as video decoder (410), video decoder (510), and video decoder (810), may be implemented using any suitable technique. In embodiments, video encoder (403), video encoder (603), and video encoder (703), as well as video decoder (410), video decoder (510), and video decoder (810) may be implemented using one or more integrated circuits. In another embodiment, the video encoder (403), video encoder (603) and video encoder (703), and video decoder (410), video decoder (510) and video decoder (810) may be implemented using one or more processors executing software instructions.

The present disclosure includes sub-block cross-component linear model prediction.

ITU-T VCEG (Q6/16) and ISO/IEC MPEG (JTC 1/SC 29/WG 11) published the h.265/HEVC (high efficiency video coding) standard in 2013 (version 1), 2014 (version 2), 2015 (version 3) and 2016 (version 4). In 2015, these two standards organizations together formed jfet (joint video exploration group) to explore the possibility to develop the next video coding standard beyond HEVC. In month 4 of 2018, jfet formally started the standardized process of next generation video coding beyond HEVC. The new standard is named universal video coding (VVC), and jfet is named joint video expert group. 7 months 2020, H.266/VVC version 1 finalized. An ad hoc panel was established to study the enhanced compression beyond VVC capability, month 1 of 2021.

To reduce cross-component redundancy, cross-component linear model (CCLM) prediction modes may be used in VVCs, for example. In the CCLM prediction mode, a chroma sample of a current CU may be predicted based on a reconstructed luma sample of the current CU by using a linear model in the following equation (1):

pred _C (i,j)＝α·rec _L ' i, j) +beta equation (1)

Wherein pred _C (i, j) may represent predicted chroma samples in the current CU, and rec _L (i, j) may represent the downsampled reconstructed luma samples of the current CU. When chroma subsampling is different from luma subsampling, such as in YCbCr422 or YCbCr420 format, a chroma CU may have a smaller size than a luma CU. Downsampling the reconstructed luma samples in the current CU may match the luma samples and the chroma samples one-to-one.

CCLM parameters (e.g., α and β) may be derived with up to 4 neighboring chroma samples and corresponding downsampled luma samples of the neighboring chroma samples. If the dimension of the current chroma block is w×h, where W is the width of the current chroma block and H is the height of the current chroma block, the width W 'of the first reference region and the height H' of the second reference region may be defined as follows:

when the LM mode is applied, W '= W, H' =h;

whenLM-amodeisapplied,w'=w+h; and

when LM-L mode is applied, H' =h+w.

The first reference region may be adjacent to a top side of the current chroma block. The second reference region may be adjacent to the left side of the current chroma block. In the LM mode, adjacent chroma samples may be located in a first reference region and a second reference region. inLM-amode,adjacentchromasamplesmaybelocatedinafirstreferenceregion. In the LM-L mode, adjacent chroma samples may be located in a second reference region.

Thus, the upper adjacent position (or position of the first reference region) may be denoted as S [0, -1] … … S [ W '-1, -1], and the left adjacent position (or position of the second reference region) may be denoted as S [ -1,0] … … S [ -1, H' -1].

Accordingly, the locations of four adjacent chroma samples may be selected as:

when the LM mode is applied and both the upper neighbor sample and the left neighbor sample are available, S [ W '/4, -1], S [3*W'/4, -1], S [ -1, H '/4], S [ -1,3 x H'/4];

whentheLM-Amodeisappliedoronlytheupperneighborsamplesareavailable,S[W'/8,-1],S[3*W'/8,-1],S[5*W'/8,-1],S[7*W'/8,-1]; and

when the LM-L mode is applied or only left neighbor samples are available, S < -1 >, H '/8 >, S < -1,3 > H'/8 >, S < -1,5 > H '/8 >, S < -1,7 > H'/8 >.

Four luma samples corresponding to four neighboring chroma samples at the selected location may be downsampled and compared four times to find two larger values: x is x ⁰ _A And x ¹ _A And two smaller values: x is x ⁰ _B And x ¹ _B . The chroma sample values of four neighboring chroma samples corresponding to four luma samples may be represented as y ⁰ _A 、y ¹ _A 、y ⁰ _B And y ¹ _B . The parameter X can be derived in equations (2) to (5) _a 、X _b 、Y _a And Y _b The following are provided:

X _a ＝(x ⁰ _A + x ¹ _A +1)>>1. equation (2)

X _b ＝(x ⁰ _B + x ¹ _B +1)>>1, a step of; equation (3)

Y _a ＝(y ⁰ _A + y ¹ _A +1)>>1, a step of; equation (4)

Y _b ＝(y ⁰ _B + y ¹ _B +1)>>1. Equation (5)

Finally, linear model parameters α and β are derived according to equations (6) and (7), respectively.

β＝Y _b -α·X _b Equation (7)

Fig. 9 illustrates an exemplary position of left and upper neighboring samples of a current block and samples of the current block involved in a CCLM prediction mode. As shown in fig. 9, the current chroma CU (902) may be of size NxN (e.g., 8x 8). The corresponding luma CU (904) of the current chroma CU (902) may be 2Nx2N (e.g., 16x 16) in size. Adjacent chroma samples of a current chroma CU (902) used to derive linear model parameters α and β may be located in a first reference region (or upper adjacent position) (906) and/or a second reference region (or left adjacent position) (908). Luminance samples corresponding to adjacent chroma samples (906) and (908) may be located in a first reference region (910) and a second reference region (912), respectively. As shown in fig. 9, luminance samples (910) and (912) are downsampled to match adjacent chrominance samples (906) and (908) one-to-one. Reconstructed values Rec 'of luminance samples (910) and (912)' _L And reconstructed values Rec of neighboring chroma samples (906) and (908) _c Can be applied to derive linear model parameters α and β based on equations (2) through (7). Once the linear model parameters α and β are obtained, the CCLM prediction mode may be used to predict chroma samples in the current chroma CU (902) based on downsampled reconstructed luma samples in the corresponding luma CU (904).

Table 1 shows an exemplary syntax for CCLM prediction. First, a CCLM mode flag (e.g., cclm_mode_flag) may be parsed (or encoded) to determine whether to apply the CCLM prediction mode to the current CU. When the CCLM mode flag (e.g., cclm_mode_flag) is 1 (or true), it indicates that the CCLM prediction mode is applied to the current CU. The CCLM mode index (e.g., cclm_mode_idx) may be further parsed to determine which CCLM mode applies to the current CU. CCLMmodesmayinclude,butarenotlimitedto,LM-AandLM-L. The LM may derive the linear model parameters α and β using the left and upper reference samples. LM-amayderivelinearmodelparametersαandβusingtheupperreferencesample,andLM-lmayderivelinearmodelparametersαandβusingtheleftreferencesample.

TABLE 1 pseudo code of CCLM

A chroma CU for CCLM applications (or a chroma CU encoded within a CCLM frame) may have spatial correlation with a spatial neighborhood. Accordingly, having (or determining) a larger CU as a CCLM block with sub-blocks inside may save signaling overhead and improve coding efficiency.

In this disclosure, a CU may include sub-blocks inside the CU, where all sub-blocks may be CCLM encoded.

In an embodiment, the partition may be based on dimensions of the CU, such as a width and/or a height of the CU. Thus, only one type of partition (e.g., horizontal or vertical) may be used in a CU. For example, if the width of a CU is equal to or greater than the height of the CU, the CU may be partitioned vertically as shown in FIG. 10A. As shown in fig. 10A, a CU (1002) may be partitioned into a plurality of sub-blocks indexed 0 to 3 in the width direction of the CU (1002). In another example, if the width of a CU is less than the height of the CU, the CU may be partitioned horizontally as shown in fig. 10B. As shown in fig. 10B, the CU (1004) may be partitioned into a plurality of sub-blocks indexed 0 to 1 in the height direction of the CU (1004).

In another embodiment, the partition may be based on a minimum sub-block size, which may be defined as minsubslick for CCLM. The value of the minimum sub-block size (e.g., minsubscclm) may be predefined in the encoder and decoder without explicit signaling. Alternatively, the minimum sub-block size (e.g., minsubscclm) may be signaled. For example, the minimum sub-block size may be signaled in a high level syntax, such as in a Sequence Parameter Set (SPS), picture Parameter Set (PPS), slice, or tile. CU may be partitioned in a horizontal direction and/or a vertical direction based on a value of a minimum sub-block size (e.g., minsubscclm). For example, if the CU (1006) is 4 in width and 8 in height, and the value of the minimum sub-block size (e.g., minsubblock cclm) is 2 (or 2x 2), the CU (1006) may be partitioned into 8 sub-blocks in the horizontal and vertical directions, which may be shown in fig. 10C.

In this disclosure, the sub-block prediction (or prediction for a sub-block) may be based on reconstructed values of previously decoded sub-blocks. The sub-block prediction may be performed in raster scan order as shown in fig. 10D. For each sub-block, reconstructed samples may be obtained by adding the residual signal to the prediction signal. The residual signal may be generated by a process including entropy decoding, inverse quantization, inverse transformation, etc. Thus, the reconstructed sample values of the previous sub-block may be used to generate predicted sample values of the subsequent sub-block.

In an embodiment, a sub-block of the current CU (such as the sub-block indexed 0 in fig. 10A) may perform CCLM using reference samples (not shown) of the current CU. Thus, the linear model parameters α and β may be derived from the reference samples of the current CU. Similarly, a subsequent sub-block (such as the sub-block with index 1 in fig. 10A) may perform CCLM using reconstructed samples of a previous sub-block (such as the sub-block with index 0) as reference samples. The linear model parameters alpha and beta may be derived based on reconstructed samples of sub-blocks with index 0. Further, the sub-block with index 2 may perform CCLM using reconstructed samples of the sub-block with index 1 as reference samples. The sub-block with index 3 may perform CCLM using reconstructed samples of the sub-block with index 2 as reference samples.

inthisdisclosure,theCCLMmode(e.g.,LM-AorLM-L)ofthesub-blocksinsidetheCUmaybethesame. In other words, once the CCLM mode is signaled using the CCLM mode index (e.g., cclm_mode_idx) as shown in table 2, all sub-blocks in the CU may apply the CCLM mode.

TABLE 2 CCLM pseudo code including CCLM mode

As shown in table 2, a CCLM mode flag (e.g., cclm_mode_flag) may be parsed (or encoded) to determine whether CCLM is applied to a current CU. If the CCLM mode flag (e.g., cclm_mode_flag) is 1 (or true), the CCLM sub-block flag (e.g., cclm_subcarrier_flag) and CCLM mode index (e.g., cclm_mode_idx) may be further parsed. The CCLM sub-block flag may indicate whether to apply CCLM to a sub-block of the current CU. theCCLMmodeindexmayindicateCCLMmodes(e.g.,LM-A,andLM-L)oftheCCLM. When the CCLM sub-block flag (e.g., cclm_sub_flag) is equal to 1 (or true), the CCLM is applied to the sub-block of the current CU. Otherwise, when the CCLM sub-block flag is not 1, CCLM is not applied to the sub-block of the current CU. The CCLM mode index (e.g., cclm_mode_idx) may be parsed to indicate which mode of the CCLM applies to the current CU (or sub-block). Thus, if the CCLM sub-block flag is not 1, the CCLM mode index may indicate which CCLM mode applies to the current CU. When the CCLM sub-block flag is 1, the CCLM mode index may indicate which CCLM mode is applied to all sub-blocks of the current CU.

In this disclosure, the CCLM mode for a sub-block or each sub-block inside a CU may depend on the availability of reference samples for the respective sub-block.

In an embodiment, as shown in fig. 10D, a gray region (1010) adjacent to the left side of the current block (1008) may represent available reference samples of the current block (1008), and a blank region (1012) adjacent to the top side of the current block (1008) may represent unavailable reference samples of the current block (1008). Thus, a sub-block with index 0 can only have a left reference sample available. Accordingly, CCLM mode LM-L may be used to derive linear model parameters α and β for sub-blocks with index 0. For sub-blocks with index 4, both left and upper reference samples are available. Thus, the sub-block with index 4 may use the CCLM mode LM.

In an embodiment, for a CCLM CU (or a CU applying CCLM) with a sub-block CCLM (or a sub-block applying CCLM), the CCLM mode index (e.g., cclm_mode_idx) may not be signaled. The CCLM mode applied to each sub-block in the CCLM CU may depend on the available reference samples of the respective sub-block. Exemplary pseudo code for skipping the CCLM mode index of a CCLM CU having a sub-block CCLM may be shown in table 3.

TABLE 3 pseudo code for skipping CCLM mode index

As shown in table 3, a CCLM mode flag (e.g., cclm_mode_flag) may be parsed (or encoded) to determine whether CCLM is applied to a current CU. If the CCLM mode flag (e.g., cclm_mode_flag) is 1 (or true), the CCLM sub-block flag (e.g., cclm_sub_flag) may be further parsed. When the CCLM sub-block flag (e.g., cclm_sub_flag) is equal to 1, it indicates that the CCLM is applied to the sub-block. Furthermore, the CCLM mode applied to each of the sub-blocks may depend on the available reference samples of the respective sub-block. Otherwise, when the CCLM sub-block flag is not equal to 1, it indicates that CCLM is not applied to the sub-block.

In another embodiment, the CCLM sub-block flag (e.g., cclm_sub_flag) may not be signaled, but rather inferred to be true at all times. Thus, when the CCLM mode (e.g., cclm_mode_flag) is equal to 1, the CCLM may also be applied to the sub-blocks of the current CU. Further, the CCLM mode applied to each of the sub-blocks may depend on the available reference samples of the respective sub-block.

Fig. 11 shows a flowchart outlining an exemplary decoding method (1100) according to some embodiments of the present disclosure. Fig. 12 shows a flowchart outlining an exemplary encoding method (1200) according to some embodiments of the present disclosure. The proposed methods may be used alone or in combination in any order. Further, each of the methods (or embodiments), encoder, and decoder may be implemented by a processing circuit (e.g., one or more processors or one or more integrated circuits). In one example, one or more processors execute a program stored in a non-volatile computer readable medium.

In embodiments, any of the operations of the methods (e.g., (1100) and (1200)) may be combined or arranged in any number or order, as desired. In an embodiment, two or more of the operations of the methods (e.g., (1100) and (1200)) may be performed in parallel.

Methods (e.g., (1100) and (1200)) may be used for reconstruction and/or encoding of a block to generate a prediction block for the block under reconstruction. In various embodiments, the methods (e.g., (1100) and (1200)) are performed by processing circuitry, such as processing circuitry in terminal devices (310), (320), (330), and (340), processing circuitry that performs the functions of video encoder (403), processing circuitry that performs the functions of video decoder (410), processing circuitry that performs the functions of video decoder (510), and processing circuitry that performs the functions of video encoder (603), and so forth. In some embodiments, the methods (e.g., (1100) and (1200)) are implemented in software instructions, so that when the processing circuitry executes the software instructions, the processing circuitry performs the methods (e.g., (1100) and (1200)).

As shown in fig. 11, the method (1100) may begin (S1101) and proceed to (S1110). At (S1110), encoded information of a current block in a current picture may be received from an encoded video bitstream.

At (S1120), the current block may be partitioned into a plurality of sub-blocks.

At (S1130), a first flag included in the encoded information may be acquired, wherein the first flag indicates whether a cross-component linear model (CCLM) prediction is applied to the current block, wherein chroma samples of the current block are predicted based on reconstructed luma samples of the current block.

At (S1140), responsive to the first flag indicating that the CCLM is applied to a current block, respective predicted sample values of chroma samples in each of the plurality of sub-blocks of the current block are determined based on the CCLM.

At (S1150), the current block may be reconstructed further based on the respective prediction sample values of the chroma samples in each of the plurality of sub-blocks of the current block.

In an example, the current block is partitioned into the plurality of sub-blocks in a width direction based on a width of the current block being equal to or greater than a height of the current block.

In method (1100), syntax elements in encoded information may be determined. The minimum sub-block size may be determined based on the syntax element. The syntax element is in one of a Sequence Parameter Set (SPS), a Picture Parameter Set (PPS), a slice, and a tile.

In some embodiments, the prediction sample values of the chroma samples in a second sub-block of the plurality of sub-blocks may be determined based on reconstructed samples of a first sub-block of the plurality of sub-blocks, the second sub-block being adjacent to the first sub-block.

In some embodiments, a second flag included in the encoded information is acquired in response to the first flag indicating that CCLM is applied to the current block. A second flag indicates whether the CCLM is applied to each of the plurality of sub-blocks. Responsive to the second flag indicating that the CCLM is applied to each of the plurality of sub-blocks, a respective predicted sample value of chroma samples in each of the plurality of sub-blocks of the current block is determined based on the CCLM.

In some embodiments, the predicted sample values of the chroma samples in a first sub-block of the plurality of sub-blocks are determined based on a first pattern of the CCLM in response to a reconstructed neighboring sample being adjacent to a left side of the first sub-block, wherein the first pattern of the CCLM indicates: the predicted sample values of the chroma samples in the first sub-block are determined based on the reconstructed neighboring samples that are neighboring the left side of the first sub-block. In response to reconstructed neighboring samples being adjacent to a left side and a top side of a second sub-block of the plurality of sub-blocks, determining the predicted sample values of the chroma samples in the second sub-block of the plurality of sub-blocks based on a second mode of the CCLM, wherein the second mode of the CCLM indicates that predicted sample values of chroma samples in a second sub-block are determined based on the reconstructed neighboring samples being adjacent to the left side and the top side of the second sub-block.

In some embodiments, a second flag included in the encoded information is obtained in response to the first flag indicating that the CCLM is applied to the current block, wherein the second flag indicates whether the CCLM is applied to each of the plurality of sub-blocks. An index included in the encoded information is obtained, wherein the index indicates a CCLM mode of the CCLM, the CCLM mode indicating which reconstructed neighboring samples the CCLM applies to generate the respective predicted sample values of the chroma samples in each of the plurality of sub-blocks. Responsive to the second flag indicating that the CCLM applies to each of the plurality of sub-blocks and the index indicating a CCLM mode, respective predicted sample values of chroma samples in each of the plurality of sub-blocks of the current block are determined based on the CCLM using the CCLM mode.

In some embodiments, responsive to the index indicating the first CCLM mode, respective predicted sample values of chroma samples in each of the plurality of sub-blocks are determined based on reconstructed neighboring samples neighboring the left and top sides of the respective one of the plurality of sub-blocks. In response to the index indicating the second CCLM mode, a respective predicted sample value of the chroma samples in each of the plurality of sub-blocks is determined based on reconstructed neighboring samples that are adjacent to a left side of a respective one of the plurality of sub-blocks. In response to the index indicating a third CCLM mode, respective predicted sample values of chroma samples in each of a plurality of sub-blocks are determined based on reconstructed neighboring samples neighboring the top side of the respective one of the plurality of sub-blocks.

As shown in fig. 12, the method (1200) may start from (S1201) and proceed to (S1210). At (S1210), a current block in a current picture may be partitioned into a plurality of sub-blocks.

At (S1220), respective prediction sample values of chroma samples in each of a plurality of sub-blocks of the current block may be determined based on a Cross Component Linear Model (CCLM) prediction, wherein the chroma samples of the current block are predicted based on reconstructed luma samples of the current block.

At (S1230), intra prediction may be performed on the current block based on respective prediction sample values of chroma samples in each of a plurality of sub-blocks of the current block.

At (S1240), a first flag indicating that the CCLM is applied to a plurality of sub-blocks of a current block may be generated.

The techniques described above may be implemented as computer software using computer-readable instructions and physically stored in one or more computer-readable media. For example, FIG. 13 illustrates a computer system (1300) suitable for implementing certain embodiments of the disclosed subject matter.

The computer software may be encoded using any suitable machine code or computer language that may be compiled, linked, or the like, to create code comprising instructions that may be executed by one or more computer Central Processing Units (CPUs), graphics Processing Units (GPUs), or the like, directly or through interpretation, microcode execution, or the like.

The instructions may be executed on various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smart phones, gaming devices, internet of things devices, and the like.

The components shown in fig. 13 for computer system (1300) are exemplary in nature, and are not intended to suggest any limitation as to the scope of use or functionality of computer software implementing embodiments of the present disclosure. Nor should the configuration of components be construed as having any dependency or requirement relating to any one or combination of components illustrated in the exemplary embodiment of the computer system (1300).

The computer system (1300) may include some human interface input devices. Such human interface input devices may be responsive to input by one or more human users through, for example, tactile input (such as, for example, key strokes, swipes, data glove movements), audio input (such as, for example, speech, beats), visual input (such as, for example, gestures), olfactory input (not shown). The human interface device may also be used to capture certain media that are not necessarily directly related to the conscious input of a person, such as audio (such as speech, music, ambient sound), images (such as scanned images, photographic images acquired from still image cameras), video (such as two-dimensional video, three-dimensional video including stereoscopic video).

The input human interface device may include one or more of the following (only one is depicted for each): a keyboard (1301), a mouse (1302), a touch pad (1303), a touch screen (1310), a data glove (not shown), a joystick (1305), a microphone (1306), a scanner (1307), and a camera (1308).

The computer system (1300) may also include some human interface output devices. Such human interface output devices may stimulate the sensation of one or more human users by, for example, tactile output, sound, light, and smell/taste. Such human interface output devices may include haptic output devices (e.g., touch screen (1310), data glove (not shown) or joystick (1305) haptic feedback, but there may also be haptic feedback devices that do not serve as input devices), audio output devices (such as: speaker (1309), headphones (not depicted)), visual output devices (such as screen (1310), including CRT screen, LCD screen, plasma screen, OLED screen, each with or without touch screen input capability, each with or without haptic feedback capability-some of which can output two-dimensional visual output or more than three-dimensional output by way of such as stereoscopic output, virtual reality glasses (not depicted), holographic display and smoke canister (not depicted)), and printers (not depicted).

The computer system (1300) may also include human-accessible storage devices and their associated media such as optical media including media (1321) such as CD/DVD ROM/RW (1320) with CD/DVD, thumb drive (1322), removable hard drive or solid state drive (1323), traditional magnetic media such as magnetic tape and floppy disk (not depicted), special ROM/ASIC/PLD based devices such as secure dongles (not depicted), and the like.

It should also be appreciated by those skilled in the art that the term "computer readable medium" as used in connection with the presently disclosed subject matter does not include transmission media, carrier waves or other volatile signals.

The computer system (1300) may also include an interface (1354) to one or more communication networks (1355). The network may be wireless, wired, optical, for example. The network may also be local, wide area, metropolitan, vehicular and industrial, real-time, delay tolerant, and so on. Examples of networks include local area networks such as ethernet, wireless LAN, cellular networks including GSM, 3G, 4G, 5G, LTE, etc., TV wired or wireless wide area digital networks including cable TV, satellite TV and terrestrial broadcast TV, vehicular and industrial networks including CAN bus, etc. Some networks typically require an external network interface adapter (such as, for example, a USB port of a computer system (1300)) that attaches to some general data port or peripheral bus (1349); other networks are typically integrated into the core of the computer system (1300) by attaching to a system bus as described below (e.g., an ethernet interface into a PC computer system or a cellular network interface into a smart phone computer system). Using any of these networks, the computer system (1300) may communicate with other entities. Such communication may be unidirectional reception only (e.g., broadcast TV), unidirectional transmission only (e.g., CANbus to some CANbus devices), or bidirectional, e.g., to other computer systems using a local area digital network or a wide area digital network. Certain protocols and protocol stacks may be used on each of those networks and network interfaces described above.

The human interface device, human accessible storage device, and network interface described above may be attached to a core (1340) of a computer system (1300).

The core (1340) may include one or more Central Processing Units (CPUs) (1341), graphics Processing Units (GPUs) (1342), special purpose programmable processing units in the form of Field Programmable Gate Arrays (FPGAs) (1343), hardware accelerators (1344) for certain tasks, graphics adapters (1350), and the like. These devices, along with Read Only Memory (ROM) (1345), random access memory (1346), internal mass storage (1347) such as internal non-user accessible hard disk drives, SSDs, etc., may be connected by a system bus (1348). In some computer systems, the system bus (1348) may be accessed in the form of one or more physical plugs to enable expansion by additional CPUs, GPUs, and the like. Peripheral devices may be attached to the system bus (1348) of the core either directly or through a peripheral bus (1349). In one example, screen (1310) may be connected to graphics adapter (1350). The architecture of the peripheral bus includes PCI, USB, etc.

The CPU (1341), GPU (1342), FPGA (1343), and accelerator (1344) may execute certain instructions, a combination of which may constitute the computer code described above. The computer code may be stored in ROM (1345) or RAM (1346). The transition data may also be stored in RAM (1346), while the permanent data may be stored in, for example, internal mass storage (1347). Fast storage and retrieval of any memory device may be enabled by using cache memory, which may be closely associated with one or more CPUs (1341), GPUs (1342), mass storage (1347), ROMs (1345), RAMs (1346), and the like.

The computer-readable medium may have computer code thereon for performing various computer-implemented operations. The media and computer code may be those specially designed and constructed for the purposes of the present disclosure, or they may be of the kind well known and available to those having skill in the computer software arts.

By way of example, and not limitation, computer system (1300) having an architecture, and in particular core (1340), may provide functionality as a result of one or more processors (including CPU, GPU, FPGA, accelerators, etc.) executing software embodied in one or more tangible computer-readable media. Such computer readable media may be media associated with mass storage accessible to the user as described above, as well as some memory of the core (1340) having non-volatile properties, such as mass storage internal to the core (1347) or ROM (1345). Software implementing various embodiments of the present disclosure may be stored in such devices and executed by cores (1340). The computer-readable medium may include one or more memory devices or chips according to particular needs. The software may cause the core (1340) and in particular the processor therein (including CPU, GPU, FPGA, etc.) to perform certain methods or certain portions of certain processes described herein, including defining data structures stored in RAM (1346) and modifying such data structures according to the processes defined by the software. Additionally or alternatively, the computer system may provide functionality as a result of logic hardwired or otherwise embodied in circuitry (e.g., accelerator (1344)), which may operate in place of or in conjunction with software to perform certain methods or certain portions of certain processes described herein. References to software may include logic, and vice versa, where appropriate. References to computer-readable media may include circuitry, such as an Integrated Circuit (IC), embodying logic for execution, or both, storing software for execution, where appropriate. The present disclosure includes any suitable combination of hardware and software.

Appendix a: acronyms

JEM: combined detection model (joint exploration model)

VVC: universal video coding (versatile video coding)

BMS: benchmark set (benchmark set)

MV: motion Vector (Motion Vector)

HEVC: high-efficiency video coding (High Efficiency Video Coding)

SEI: supplementary enhancement information (Supplementary Enhancement Information)

VUI: video availability information (Video Usability Information)

GOPs: picture group (Groups of Pictures)

TUs: conversion unit (Transform Units)

PUs: prediction unit (Prediction Units)

CTUs: coding tree unit (Coding Tree Units)

CTBs: coding tree block (Coding Tree Blocks)

PBs: prediction block (Prediction Blocks)

HRD: suppose a reference decoder (Hypothetical Reference Decoder)

SNR: signal to noise ratio (Signal Noise Ratio)

CPUs: central processing unit (Central Processing Units)

GPUs: graphic processing unit (Graphics Processing Units)

CRT: cathode Ray Tube (Cathode Ray Tube)

LCD: LCD Display (Liquid-Crystal Display)

OLED: organic Light-Emitting Diode (Organic Light-Emitting Diode)

CD: compression plate (Compact Disc)

DVD: digital video disc (Digital Video Disc)

ROM: read-Only Memory (Read-Only Memory)

RAM: random access memory (Random Access Memory)

ASIC: application specific integrated circuit (Application-Specific Integrated Circuit)

PLD: programmable logic device (Programmable Logic Device)

LAN: local area network (Local Area Network)

GSM: global mobile communication system (Global System for Mobile communications)

LTE: long Term Evolution (Long-Term Evolution)

CANBus: controller area network bus (Controller Area Network Bus)

USB: universal serial bus (Universal Serial Bus)

PCI: peripheral component interconnect (Peripheral Component Interconnect)

And (3) FPGA: field programmable gate region (Field Programmable Gate Areas)

SSD: solid state drive (solid-state drive)

IC: integrated circuit (Integrated Circuit)

CU: coding Unit (Coding Unit)

While this disclosure describes several exemplary embodiments, there are alterations, permutations, and various substitute equivalents which fall within the scope of this disclosure. It will thus be appreciated that those skilled in the art will be able to devise numerous systems and methods which, although not explicitly shown or described herein, embody the principles of the disclosure and are thus within its spirit and scope.

Claims

1. A method of video decoding performed in a video decoder, the method comprising:

Receiving encoded information of a current block in a current picture from an encoded video bitstream;

partitioning the current block into a plurality of sub-blocks;

obtaining a first flag included in the encoded information, the first flag indicating whether a cross-component linear model (CCLM) prediction is applied to the current block, wherein chroma samples of the current block are predicted based on reconstructed luma samples of the current block;

responsive to the first flag indicating that the CCLM applies to the current block, determining, based on the CCLM, respective predicted sample values for the chroma samples in each of the plurality of sub-blocks of the current block; and

reconstructing the current block based on the respective predicted sample values of the chroma samples in each of the plurality of sub-blocks of the current block.

2. The method of claim 1, wherein the partitioning the current block further comprises:

the current block is partitioned into the plurality of sub-blocks in a width direction based on a width of the current block being equal to or greater than a height of the current block.

3. The method of claim 1, wherein the partitioning the current block further comprises:

The current block is partitioned into the plurality of sub-blocks in a height direction based on a width of the current block being smaller than a height of the current block.

4. The method of claim 1, wherein the partitioning the current block further comprises:

the current block is partitioned into the plurality of sub-blocks having a minimum sub-block size in a height direction and a width direction.

5. The method as recited in claim 4, further comprising:

acquiring syntax elements in the encoded information; and

determining the minimum sub-block size based on the syntax element, wherein:

the syntax element is in one of a Sequence Parameter Set (SPS), a Picture Parameter Set (PPS), a slice, and a tile.

6. The method of claim 1, wherein the determining further comprises:

the prediction sample values of the chroma samples in a second sub-block of the plurality of sub-blocks are determined based on reconstructed samples of a first sub-block of the plurality of sub-blocks, the second sub-block being adjacent to the first sub-block.

7. The method of claim 1, wherein the determining further comprises:

in response to the first flag indicating that the CCLM is applied to the current block,

Obtaining a second flag included in the encoded information, the second flag indicating whether the CCLM is applied to each of the plurality of sub-blocks; and

in response to the second flag indicating that the CCLM is applied to each of the plurality of sub-blocks, the respective predicted sample values of the chroma samples in each of the plurality of sub-blocks of the current block are determined based on the CCLM.

8. The method of claim 7, wherein the determining the corresponding predicted sample value further comprises:

responsive to a reconstructed neighboring sample being adjacent to a left side of a first sub-block of the plurality of sub-blocks, determining the predicted sample value of the chroma samples in the first sub-block of the plurality of sub-blocks based on a first pattern of the CCLM, the first pattern of the CCLM indicating: determining the predicted sample values for the chroma samples in the first sub-block based on the reconstructed neighboring samples that are neighboring the left side of the first sub-block; and

in response to reconstructed neighboring samples being adjacent to a left side and a top side of a second sub-block of the plurality of sub-blocks, the predicted sample values of the chroma samples in the second sub-block of the plurality of sub-blocks are determined based on a second mode of the CCLM, the second mode of the CCLM indicating the predicted sample values of the chroma samples in the second sub-block are determined based on the reconstructed neighboring samples being adjacent to the left side and the top side of the second sub-block.

9. The method of claim 1, wherein the determining further comprises:

obtaining a second flag included in the encoded information, the second flag indicating whether the CCLM is applied to each of the plurality of sub-blocks;

obtaining an index included in the encoded information, the index indicating a CCLM mode of the CCLM, the CCLM mode indicating which reconstructed neighboring samples the CCLM applies to generate the respective predicted sample values of the chroma samples in each of the plurality of sub-blocks; and

in response to the second flag indicating that the CCLM applies to each of the plurality of sub-blocks and the index indicates the CCLM mode, the respective predicted sample value of the chroma samples in each of the plurality of sub-blocks of the current block is determined based on the CCLM using the CCLM mode.

10. The method of claim 9, wherein the determining further comprises:

responsive to the index indicating a first CCLM mode, determining the respective predicted sample values of the chroma samples in each of the plurality of sub-blocks based on reconstructed neighboring samples neighboring a left side and a top side of the respective one of the plurality of sub-blocks;

Responsive to the index indicating a second CCLM mode, determining the respective predicted sample values of the chroma samples in each of the plurality of sub-blocks based on the reconstructed neighboring samples neighboring the left side of the respective one of the plurality of sub-blocks; and

in response to the index indicating a third CCLM mode, the respective predicted sample value of the chroma samples in each of the plurality of sub-blocks is determined based on the reconstructed neighboring samples neighboring the top side of the respective one of the plurality of sub-blocks.

11. An apparatus, comprising:

processing circuitry configured to:

partitioning the current block into a plurality of sub-blocks;

12. The device of claim 11, wherein the processing circuit is further configured to:

13. The device of claim 11, wherein the processing circuit is further configured to:

14. The device of claim 11, wherein the processing circuit is further configured to:

15. The device of claim 14, wherein the processing circuit is further configured to:

acquiring syntax elements in the encoded information; and

determining the minimum sub-block size based on the syntax element, wherein:

16. The device of claim 11, wherein the processing circuit is further configured to:

17. The device of claim 11, wherein the processing circuit is further configured to:

18. The device of claim 17, wherein the processing circuit is further configured to:

19. The device of claim 11, wherein the processing circuit is further configured to:

20. The device of claim 19, wherein the processing circuit is further configured to: